Variable-current generator



Nov. 27 1923.

c. A. HOXIE VARIABLE CURRENT GENERATOR Filed May 20, 1921 L mmmInx/ntor-Z Charies A. Hoxie, y M

, His Attorney.

I Patented Nov. V I

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Be it known that I, Cmnms A. Hoxm, a citizen of the United States,residmg at schenectaldly, in the county of Schenectady, State of ewYork, have invented certam' new and useful Improvements in Variable-'Current Generators, of which the following is a specification.

Thls invention relates to a method and ap aratus for producing varyingcurrents or vo tages and is articular ly app icable to the reduction ofa ternating or pulsating currents or voltages having any desired waveform. "I 2" ,One object of my invention is to provide pe wherein. theamount of current or vo tage produced at any instant'is controlled b ascreen placed of light trave ing from a v suita aphotmelectric cell.This screen is provid with specially .formed cut-way or transparentportions and is arthat thelight whichpasses through these ortions andalls upon the photo-electric ce is causedto varyin amanner correspondingto the variation to produce in the current able source to r v g 1 Thereferre'dform of the apparatus c0n structe in accordance withparticularly adapted for the currentsor voltages which vary throu hperiodic cycles and it may thus be used or the of current or voltages ofure sine waves. Means are also providedw ereby the frequenc as well asthe form of such waves may be c an ed as desired.

Other objects an advantagesof my invention will appear from'thefollowing description taken in connection with the-accompanyingdrawings, wherein Fig.1 is a diagrammatic view of an apparatus consstructed in accordance with my invention, and'Fig. 2 is a showing indetailof meansfor controlling the passage of light to the photo-electriccell 'so that currentsjqfsine wave form are produced. 3

Referring to Fig. 1 of thedrawing, A represents a'source of light, B aphoto.- electric cell and C 'thermionic vacuum tube amplifier. Lightfrom-the source [A passes through a lens 10, ,gpenings in'the dis 11 andscreen 12 hereinafter morefully tofbe described and thence to thejcellB. i I

is cell may be conveniently made by condensation over t Iode.

be conveniently, operated at a my invention isproduc'tmn of 18 81.lerill No. 71,280. I

exhausting a tube evaporating within the same a quantity of-metallicotassium which is condensed upon the wa a suitable barrier beingprovided to revent its I e surface w "ch is intended to act as ,awindow. 100 microns of hydrogen are then admitted to the tube and the liht sensitive potassium tube is 'forme by connecting the tube in serieswith a resistance of about 10000 ohms to a 500 volt source of potentialwhich will pass about 33 milli-amp'eres through the tube in the form ofa bluish discharge. .In this 0peratlon the potassium constitutes thecathsensitiveness may be still further increased by introducing new hdrogen and again submitting the tube to] ischargc. Finally the hydrogenis removed and argon gas is ad- Theiresult produced is an increase m thesensitiveness of the, tube. If desired the mitted,- the pressure ofthisvarying according to working conditions from 1111010118. Lower pressuresare used with higher increases in potentials to give thev tube a greaterstability. "Such a tube may potential which is between 50 and 500 volts.If desired toincrease the sensitivity more argon 7 may be admitted. 7

When this cell is placed, in series with a suitable source of potentialthe current through the cell is dependent upon the quantity of lightfalling upon the cathodeorthe --area of cathode surface illuminated.While I- have shown and described one form of photo-electric cell, it isclear that other forms may be used.-- I intend that the termphoto-electric cell shall apply to a device of this type which isadapted to be included in an electric circuit and has the property ofchanging the current passing therethrough in proportion to any change inthe quantrtyof area of I illumination to which the cell 1s subjectedregardless of the rapidwith which the change in illumination is it eected. The cell-I employ should be aiso substantially free frominductance -or capacity. The screen in the form of invention shown inFig. 2 isfprovided with-an open-'- ing 14 to ermit passage-of light intothe cell B. T e shape-of this opening varies with the term of wave-it isdesired to-produce' and in-the present instance is offa form to give asine wave. The; edges of the openings are each of the form right andleft.

of a sine curve. The disc 11 likewise interposed in the girth of lightfrom the source A to the cell is mounted to rotate about anaxis 15 andis adapted to be actuated by a motor 16 which may be controlled to runat any desired speed. The disc 11 in the form shown is provided with aseries of openings 17 near its outer edge which are approximatelyrectangular in form and are spaced apart from one another by a dlstanceequal to the width of an opening.

The effect of the rotation of the disc 11 in front of the opening 14 isto cause a beam of light of the form in cross section of one of 15 theopenings 17 to pass across the opening 14 at a unlforl'n rate producinga definite variation in the quantity of light entering the cell and aresulting proportional vanation in the current through the cell. In theform shown I have provided a rectangular opening in the disc 11 and acurved opcnin in the screen 12. The same results woul however, beeffected by making the opening in the Screen rectangular andatheopenings in the disc of the special form to give the desired wave. Inconnection with the form of openings in the disc and screen it'is to benoted that the desired wave form is determined merely by the quantity oflight which enters the cell B from instant to instant. It will thus beseen that various forms of openings will effect this result, the solecondition being that the change in area per unit distance in thedirection of motion be thesame. While I have shown the disc 11 providedwith openings 17 as a means for causing the light to pass over theopening 14 it iS obvious however that other. means may be employed, suchfor example as a rotatlng mirror.

The circuit through the cell B includes a battery 18 and a non-inductiveresistance 19, this circuit being in electrical connection with the grid20 of the amplifier C from a point 21 intermediate the resistance 19 andanode 8. The filament 22 is connected to the opposite end of resistance19 preferably through a few battery c ll 23 to maintain a properdifference of potential between the filament andgrid. In certain casesthe potential difi'erence across the terminals of the resistance 19 willbe such' as to make the use of these battery cells unnecessary. Includedin the plate circuit of the amplifier is a source of current and anon-inductive resistance 24 to the ends of which are connected theterminals 25 and 26. While I have shown as an amplifier a pliotron, itis obvious that other forms of amplifiers may be used, such for example,as a dynatron. In any such case the photo-electric cell will be arrangedso as to affect the control circuit of the amplifier.

, From the above it will be seen oration a pulsating voltage of that nopthe desired without appreciable inductance ma netic or electrostaticfields. fiat I A oordance with the shape of the light controllinopenings is the use of a photo-electric cell which produces changes incurrent corresponding strictly to changes in the area illuminated andthe use of electric circuits or capacity. Because of the latter featuremy device may be employed without danger of interference to neighboringinstruments because of stray claim as new and desire to secure byLetters Patent of the United States is:

1. The method of producing voltage or current waves of predeterminedform by means of a photo-electric device having a light sensitivecathode which consists in causing the cross sectional area of a beam oflight directed on said cathode to undergo variations corresponding tocomplete cycles of the desired voltage or current waves.

2. The method of producing voltage or current waves of predeterminedform by means of a photo-electric device having a light sensitivecathode which consists in directing a beam of light upon said cathode,causing the beam to undergo cycles of variations in cross sectional areacorresponding to complete cycles of the voltage or current wave desired,and amplifying said waves.

In a device for producing voltage or current waves having apredetermined definite form, the combination of a photo-electric device,means for directing a beam of light toward said device, and meanscomprising a pair of cooperating relatively. movable members for varyingthe cross-sectional area of said beam in accordance with the form of thewaves to be produced.

4. In a device for producing voltage or current waves having apredetermined definite form, the combination of a photo-electric device,'means for directing a-beam of light toward said device, and a pair ofrelatively movable members arranged in the path of said beam, saidmembers having registerable openings for varying the cross sectionalarea of said beam in accordance with the desired form of wave to beproduced. 125

, 5. A device for producing periodic voltage or current waves having adefinite predetermined form comprising a photo-electric device having alight sensitive cathode,

a 'circuit including a source of energy connected to said device,asource of light, means for directing a beam of light from said sourceonto said cathode, a screen and a rotatable disk each arranged in thepath of 5 said .beam of light, said disk having a plurality ofsubstantially rectangular openings therein and said screen having anopening constructed to cooperate with eachgopening in'said disk topermit the passage of said beam and to vary the cross sectional 10 areathereof in proportion to the afnplitude of the instantaneous values ofthe voltage or current waves to be produced.

In'witnes s whereof I have hereunto set my hand this 18th da. of Max,1921.

CHA LES HOXIE.

